[Tex/LaTex] Vertical space between align and alignat environments

alignequationsspacingvertical alignment

I have a problem with the vertical space between align (1) and alignat (2). How can I reduce this space to the same vertical space as before (1)? How can I completely erase the vertical space? I know I can do this globally with abovedisplayskip and belowdisplayskip, but it doesn't work simply within these environments and I don't want to change anything globally.

Here is the MWE:

\documentclass[a4paper, 12pt, headsepline]{scrreprt}
\usepackage[onehalfspacing]{setspace}
\usepackage{amsmath, amssymb, mathtools}
\usepackage{mathptmx}
\usepackage[a4paper]{geometry}
\geometry{left=2cm,right=5cm,top=2cm,bottom=2cm}


\begin{document}
Text text Text text Text text Text text Text text Text text Text text Text text Text text Text text Text text Text text Text text Text text Text text Text text Text text
\begin{align}
X_{t+1} &=  \frac{Z_{t+1}+X_{t+1}}{Y_M}  \\
N_{t}  &=  \frac{X_{t+1}+X_{t+1}}{T_{t+1}} \notag 
\end{align} 
% Reduce the vertical space here. Ideally to the same distance as from align to the above text, or whatever there is (eg other environments?)
\begin{alignat}{3}
&\text{as:} \quad & \gamma_{xyz} = \frac{a} {b} \qquad & \text{and}  & \qquad      \gamma_{zhk} = \frac{b}{a} \notag
\end{alignat}
Text text Text text Text text Text text Text text Text text Text text Text text Text text Text text Text text Text text Text text Text text Text text Text text Text text
\end{document}

As you can see, there is an undesired, too big vertical space between align and alignat.

Best Answer

I wouldn't mess with it. It looks just fine if you put as: between the two environments:

\documentclass{scrreprt}

\usepackage{amsmath}

\begin{document}

\noindent Text before.
\begin{align}
  X_{t+1} &= \frac{Z_{t+1} + X_{t+1}}{Y_{M}}\\
  N_{t}   &= \frac{X_{t+1} + X_{t+1}}{T_{t+1}}\notag
\end{align}
as
\begin{equation*}
  \gamma_{xyz} = \frac{a}{b}
  \qquad \text{and} \qquad
  \gamma_{zhk} = \frac{b}{a}
\end{equation*}
Text after.

\end{document}

output

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